| blob | eb65795e913e9eb6c3a6360568c3f393dc8beacb |
1 /* Fold a constant sub-tree into a single node for C-compiler
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
3 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
20 02111-1307, USA. */
22 /*@@ This file should be rewritten to use an arbitrary precision
23 @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
24 @@ Perhaps the routines could also be used for bc/dc, and made a lib.
25 @@ The routines that translate from the ap rep should
26 @@ warn if precision et. al. is lost.
27 @@ This would also make life easier when this technology is used
28 @@ for cross-compilers. */
30 /* The entry points in this file are fold, size_int_wide, size_binop
31 and force_fit_type.
33 fold takes a tree as argument and returns a simplified tree.
35 size_binop takes a tree code for an arithmetic operation
36 and two operands that are trees, and produces a tree for the
37 result, assuming the type comes from `sizetype'.
39 size_int takes an integer value, and creates a tree constant
40 with type from `sizetype'.
42 force_fit_type takes a constant and prior overflow indicator, and
43 forces the value to fit the type. It returns an overflow indicator. */
62 HOST_WIDE_INT));
65 HOST_WIDE_INT *));
90 HOST_WIDE_INT *,
112 static tree fold_binary_op_with_conditional_arg
119 /* The following constants represent a bit based encoding of GCC's
120 comparison operators. This encoding simplifies transformations
121 on relational comparison operators, such as AND and OR. */
122 #define COMPCODE_FALSE 0
123 #define COMPCODE_LT 1
124 #define COMPCODE_EQ 2
125 #define COMPCODE_LE 3
126 #define COMPCODE_GT 4
127 #define COMPCODE_NE 5
128 #define COMPCODE_GE 6
129 #define COMPCODE_TRUE 7
131 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
132 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
133 and SUM1. Then this yields nonzero if overflow occurred during the
134 addition.
136 Overflow occurs if A and B have the same sign, but A and SUM differ in
137 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
138 sign. */
139 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
140 \f
141 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
142 We do that by representing the two-word integer in 4 words, with only
143 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
144 number. The value of the word is LOWPART + HIGHPART * BASE. */
146 #define LOWPART(x) \
147 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
148 #define HIGHPART(x) \
149 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
150 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
152 /* Unpack a two-word integer into 4 words.
153 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
154 WORDS points to the array of HOST_WIDE_INTs. */
156 static void
160 HOST_WIDE_INT hi;
161 {
166 }
168 /* Pack an array of 4 words into a two-word integer.
169 WORDS points to the array of words.
170 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
172 static void
177 {
180 }
181 \f
182 /* Make the integer constant T valid for its type by setting to 0 or 1 all
183 the bits in the constant that don't belong in the type.
185 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
186 nonzero, a signed overflow has already occurred in calculating T, so
187 propagate it. */
189 int
191 tree t;
193 {
195 HOST_WIDE_INT high;
199 {
200 /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
201 Consider doing it via real_convert now. */
203 }
213 else
216 /* First clear all bits that are beyond the type's precision. */
219 ;
223 else
224 {
228 }
230 /* Unsigned types do not suffer sign extension or overflow unless they
231 are a sizetype. */
237 /* If the value's sign bit is set, extend the sign. */
245 {
246 /* Value is negative:
247 set to 1 all the bits that are outside this type's precision. */
251 else
252 {
256 }
257 }
259 /* Return nonzero if signed overflow occurred. */
260 return
263 }
264 \f
265 /* Add two doubleword integers with doubleword result.
266 Each argument is given as two `HOST_WIDE_INT' pieces.
267 One argument is L1 and H1; the other, L2 and H2.
268 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
270 int
276 {
278 HOST_WIDE_INT h;
286 }
288 /* Negate a doubleword integer with doubleword result.
289 Return nonzero if the operation overflows, assuming it's signed.
290 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
291 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
293 int
296 HOST_WIDE_INT h1;
299 {
301 {
305 }
306 else
307 {
311 }
312 }
313 \f
314 /* Multiply two doubleword integers with doubleword result.
315 Return nonzero if the operation overflows, assuming it's signed.
316 Each argument is given as two `HOST_WIDE_INT' pieces.
317 One argument is L1 and H1; the other, L2 and H2.
318 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
320 int
326 {
341 {
344 {
346 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
348 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
352 }
354 }
358 /* Check for overflow by calculating the top half of the answer in full;
359 it should agree with the low half's sign bit. */
362 {
365 }
367 {
370 }
372 }
373 \f
374 /* Shift the doubleword integer in L1, H1 left by COUNT places
375 keeping only PREC bits of result.
376 Shift right if COUNT is negative.
377 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
378 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
380 void
388 {
392 {
395 }
397 #ifdef SHIFT_COUNT_TRUNCATED
400 #endif
403 {
404 /* Shifting by the host word size is undefined according to the
405 ANSI standard, so we must handle this as a special case. */
408 }
410 {
413 }
414 else
415 {
419 }
421 /* Sign extend all bits that are beyond the precision. */
429 ;
431 {
434 }
435 else
436 {
440 }
441 }
443 /* Shift the doubleword integer in L1, H1 right by COUNT places
444 keeping only PREC bits of result. COUNT must be positive.
445 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
446 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
448 void
456 {
459 signmask = (arith
463 #ifdef SHIFT_COUNT_TRUNCATED
466 #endif
469 {
470 /* Shifting by the host word size is undefined according to the
471 ANSI standard, so we must handle this as a special case. */
474 }
476 {
479 }
480 else
481 {
485 }
487 /* Zero / sign extend all bits that are beyond the precision. */
490 {
493 }
495 ;
497 {
500 }
501 else
502 {
506 }
507 }
508 \f
509 /* Rotate the doubleword integer in L1, H1 left by COUNT places
510 keeping only PREC bits of result.
511 Rotate right if COUNT is negative.
512 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
514 void
521 {
533 }
535 /* Rotate the doubleword integer in L1, H1 left by COUNT places
536 keeping only PREC bits of result. COUNT must be positive.
537 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
539 void
546 {
558 }
559 \f
560 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
561 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
562 CODE is a tree code for a kind of division, one of
563 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
564 or EXACT_DIV_EXPR
565 It controls how the quotient is rounded to an integer.
566 Return nonzero if the operation overflows.
567 UNS nonzero says do unsigned division. */
569 int
576 HOST_WIDE_INT hnum_orig;
578 HOST_WIDE_INT hden_orig;
581 {
597 /* calculate quotient sign and convert operands to unsigned. */
599 {
601 {
603 /* (minimum integer) / (-1) is the only overflow case. */
607 }
609 {
612 }
613 }
618 /* This unsigned division rounds toward zero. */
621 }
625 /* hden != 0 already checked. */
630 }
640 /* Special code for when the divisor < BASE. */
642 {
643 /* hnum != 0 already checked. */
645 {
649 }
650 }
651 else
652 {
653 /* Full double precision division,
654 with thanks to Don Knuth's "Seminumerical Algorithms". */
658 /* Find the highest nonzero divisor digit. */
661 {
664 }
666 /* Insure that the first digit of the divisor is at least BASE/2.
667 This is required by the quotient digit estimation algorithm. */
674 {
678 }
683 {
688 }
689 }
693 /* Main loop */
695 {
696 /* Guess the next quotient digit, quo_est, by dividing the first
697 two remaining dividend digits by the high order quotient digit.
698 quo_est is never low and is at most 2 high. */
705 else
708 /* Refine quo_est so it's usually correct, and at most one high. */
713 quo_est--;
715 /* Try QUO_EST as the quotient digit, by multiplying the
716 divisor by QUO_EST and subtracting from the remaining dividend.
717 Keep in mind that QUO_EST is the I - 1st digit. */
721 {
727 }
729 /* If quo_est was high by one, then num[i] went negative and
730 we need to correct things. */
732 {
733 quo_est--;
736 {
740 }
743 }
745 /* Store the quotient digit. */
747 }
748 }
752 finish_up:
753 /* if result is negative, make it so. */
757 /* compute trial remainder: rem = num - (quo * den) */
763 {
772 {
773 /* quo = quo - 1; */
776 }
777 else
784 {
787 }
788 else
794 {
800 /* Get absolute values */
806 /* If (2 * abs (lrem) >= abs (lden)) */
815 {
817 /* quo = quo - 1; */
820 else
821 /* quo = quo + 1; */
824 }
825 else
827 }
832 }
834 /* compute true remainder: rem = num - (quo * den) */
839 }
840 \f
841 /* Determine whether an expression T can be cheaply negated using
842 the function negate_expr. */
844 static bool
846 tree t;
847 {
850 tree type;
859 {
864 /* Check that -CST will not overflow type. */
867 {
872 }
873 else
886 }
888 }
890 /* Given T, an expression, return the negation of T. Allow for T to be
891 null, in which case return null. */
893 static tree
895 tree t;
896 {
897 tree type;
898 tree tem;
907 {
920 /* - (A - B) -> B - A */
930 }
933 }
934 \f
935 /* Split a tree IN into a constant, literal and variable parts that could be
936 combined with CODE to make IN. "constant" means an expression with
937 TREE_CONSTANT but that isn't an actual constant. CODE must be a
938 commutative arithmetic operation. Store the constant part into *CONP,
939 the literal in *LITP and return the variable part. If a part isn't
940 present, set it to null. If the tree does not decompose in this way,
941 return the entire tree as the variable part and the other parts as null.
943 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
944 case, we negate an operand that was subtracted. Except if it is a
945 literal for which we use *MINUS_LITP instead.
947 If NEGATE_P is true, we are negating all of IN, again except a literal
948 for which we use *MINUS_LITP instead.
950 If IN is itself a literal or constant, return it as appropriate.
952 Note that we do not guarantee that any of the three values will be the
953 same type as IN, but they will have the same signedness and mode. */
955 static tree
957 tree in;
961 {
968 /* Strip any conversions that don't change the machine mode or signedness. */
975 /* We can associate addition and subtraction together (even
976 though the C standard doesn't say so) for integers because
977 the value is not affected. For reals, the value might be
978 affected, so we can't. */
981 {
987 /* First see if either of the operands is a literal, then a constant. */
998 /* If we haven't dealt with either operand, this is not a case we can
999 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1004 else
1007 /* Now do any needed negations. */
1014 }
1017 else
1021 {
1028 }
1031 }
1033 /* Re-associate trees split by the above function. T1 and T2 are either
1034 expressions to associate or null. Return the new expression, if any. If
1035 we build an operation, do it in TYPE and with CODE. */
1037 static tree
1041 tree type;
1042 {
1048 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1049 try to fold this since we will have infinite recursion. But do
1050 deal with any NEGATE_EXPRs. */
1053 {
1055 {
1062 }
1064 }
1067 }
1068 \f
1069 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1070 to produce a new constant.
1072 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1074 static tree
1079 {
1083 HOST_WIDE_INT hi;
1085 HOST_WIDE_INT garbageh;
1086 tree t;
1089 int is_sizetype
1100 {
1120 /* It's unclear from the C standard whether shifts can overflow.
1121 The following code ignores overflow; perhaps a C standard
1122 interpretation ruling is needed. */
1152 /* This is a shortcut for a common special case. */
1157 {
1163 }
1165 /* ... fall through ... */
1169 {
1172 }
1175 {
1178 }
1185 /* This is a shortcut for a common special case. */
1190 {
1195 }
1197 /* ... fall through ... */
1213 else
1219 else
1225 }
1227 /* If this is for a sizetype, can be represented as one (signed)
1228 HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
1229 constants. */
1235 else
1236 {
1239 }
1242 = ((notrunc
1249 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1250 So check if force_fit_type truncated the value. */
1261 }
1263 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1264 constant. We assume ARG1 and ARG2 have the same data type, or at least
1265 are the same kind of constant and the same machine mode.
1267 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1269 static tree
1274 {
1282 {
1283 REAL_VALUE_TYPE d1;
1284 REAL_VALUE_TYPE d2;
1285 REAL_VALUE_TYPE value;
1286 tree t;
1291 /* If either operand is a NaN, just return it. Otherwise, set up
1292 for floating-point trap; we return an overflow. */
1302 value));
1312 }
1314 {
1320 tree t;
1323 {
1343 notrunc),
1349 notrunc));
1353 {
1354 tree magsquared
1358 notrunc);
1361 const_binop
1366 notrunc),
1368 notrunc),
1369 notrunc),
1371 const_binop
1376 notrunc),
1378 notrunc),
1379 notrunc),
1381 }
1386 }
1388 }
1390 }
1392 /* These are the hash table functions for the hash table of INTEGER_CST
1393 nodes of a sizetype. */
1395 /* Return the hash code code X, an INTEGER_CST. */
1397 static hashval_t
1400 {
1406 }
1408 /* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
1409 is the same as that given by *Y, which is the same. */
1411 static int
1415 {
1423 }
1424 \f
1425 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1426 bits are given by NUMBER and of the sizetype represented by KIND. */
1428 tree
1430 HOST_WIDE_INT number;
1432 {
1434 }
1436 /* Likewise, but the desired type is specified explicitly. */
1440 htab_t size_htab;
1442 tree
1444 HOST_WIDE_INT number;
1445 tree type;
1446 {
1450 {
1453 }
1455 /* Adjust NEW_CONST to be the constant we want. If it's already in the
1456 hash table, we return the value from the hash table. Otherwise, we
1457 place that in the hash table and make a new node for the next time. */
1466 {
1472 }
1473 else
1475 }
1477 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1478 is a tree code. The type of the result is taken from the operands.
1479 Both must be the same type integer type and it must be a size type.
1480 If the operands are constant, so is the result. */
1482 tree
1486 {
1493 /* Handle the special case of two integer constants faster. */
1495 {
1496 /* And some specific cases even faster than that. */
1505 /* Handle general case of two integer constants. */
1507 }
1513 }
1515 /* Given two values, either both of sizetype or both of bitsizetype,
1516 compute the difference between the two values. Return the value
1517 in signed type corresponding to the type of the operands. */
1519 tree
1522 {
1524 tree ctype;
1530 /* If the type is already signed, just do the simple thing. */
1537 /* If either operand is not a constant, do the conversions to the signed
1538 type and subtract. The hardware will do the right thing with any
1539 overflow in the subtraction. */
1544 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1545 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1546 overflow) and negate (which can't either). Special-case a result
1547 of zero while we're here. */
1552 else
1555 }
1556 \f
1558 /* Given T, a tree representing type conversion of ARG1, a constant,
1559 return a constant tree representing the result of conversion. */
1561 static tree
1563 tree t;
1564 tree arg1;
1565 {
1570 {
1572 {
1573 /* If we would build a constant wider than GCC supports,
1574 leave the conversion unfolded. */
1578 /* If we are trying to make a sizetype for a small integer, use
1579 size_int to pick up cached types to reduce duplicate nodes. */
1585 /* Given an integer constant, make new constant with new type,
1586 appropriately sign-extended or truncated. */
1590 /* Indicate an overflow if (1) ARG1 already overflowed,
1591 or (2) force_fit_type indicates an overflow.
1592 Tell force_fit_type that an overflow has already occurred
1593 if ARG1 is a too-large unsigned value and T is signed.
1594 But don't indicate an overflow if converting a pointer. */
1604 }
1606 {
1607 /* Don't initialize these, use assignments.
1608 Initialized local aggregates don't work on old compilers. */
1609 REAL_VALUE_TYPE x;
1610 REAL_VALUE_TYPE l;
1611 REAL_VALUE_TYPE u;
1622 /* See if X will be in range after truncation towards 0.
1623 To compensate for truncation, move the bounds away from 0,
1624 but reject if X exactly equals the adjusted bounds. */
1628 /* If X is a NaN, use zero instead and show we have an overflow.
1629 Otherwise, range check. */
1633 && !no_upper_bound
1637 {
1641 }
1647 }
1649 }
1651 {
1655 {
1657 {
1658 /* We make a copy of ARG1 so that we don't modify an
1659 existing constant tree. */
1663 }
1674 }
1675 }
1678 }
1679 \f
1680 /* Return an expr equal to X but certainly not valid as an lvalue. */
1682 tree
1684 tree x;
1685 {
1686 tree result;
1688 /* These things are certainly not lvalues. */
1699 }
1701 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
1702 Zero means allow extended lvalues. */
1706 /* When pedantic, return an expr equal to X but certainly not valid as a
1707 pedantic lvalue. Otherwise, return X. */
1709 tree
1711 tree x;
1712 {
1715 else
1717 }
1718 \f
1719 /* Given a tree comparison code, return the code that is the logical inverse
1720 of the given code. It is not safe to do this for floating-point
1721 comparisons, except for NE_EXPR and EQ_EXPR. */
1723 static enum tree_code
1726 {
1728 {
1743 }
1744 }
1746 /* Similar, but return the comparison that results if the operands are
1747 swapped. This is safe for floating-point. */
1749 static enum tree_code
1752 {
1754 {
1768 }
1769 }
1772 /* Convert a comparison tree code from an enum tree_code representation
1773 into a compcode bit-based encoding. This function is the inverse of
1774 compcode_to_comparison. */
1776 static int
1779 {
1781 {
1796 }
1797 }
1799 /* Convert a compcode bit-based encoding of a comparison operator back
1800 to GCC's enum tree_code representation. This function is the
1801 inverse of comparison_to_compcode. */
1803 static enum tree_code
1806 {
1808 {
1823 }
1824 }
1826 /* Return nonzero if CODE is a tree code that represents a truth value. */
1828 static int
1831 {
1836 }
1837 \f
1838 /* Return nonzero if two operands are necessarily equal.
1839 If ONLY_CONST is nonzero, only return nonzero for constants.
1840 This function tests whether the operands are indistinguishable;
1841 it does not test whether they are equal using C's == operation.
1842 The distinction is important for IEEE floating point, because
1843 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
1844 (2) two NaNs may be indistinguishable, but NaN!=NaN. */
1846 int
1850 {
1851 /* If both types don't have the same signedness, then we can't consider
1852 them equal. We must check this before the STRIP_NOPS calls
1853 because they may change the signedness of the arguments. */
1861 /* This is needed for conversions and for COMPONENT_REF.
1862 Might as well play it safe and always test this. */
1868 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
1869 We don't care about side effects in that case because the SAVE_EXPR
1870 takes care of that for us. In all other cases, two expressions are
1871 equal if they have no side effects. If we have two identical
1872 expressions with side effects that should be treated the same due
1873 to the only side effects being identical SAVE_EXPR's, that will
1874 be detected in the recursive calls below. */
1880 /* Next handle constant cases, those for which we can return 1 even
1881 if ONLY_CONST is set. */
1884 {
1897 {
1907 {
1912 }
1915 }
1919 only_const)
1921 only_const));
1934 }
1940 {
1942 /* Two conversions are equal only if signedness and modes match. */
1958 /* For commutative ops, allow the other order. */
1971 /* If either of the pointer (or reference) expressions we are dereferencing
1972 contain a side effect, these cannot be equal. */
1978 {
2000 }
2009 }
2010 }
2011 \f
2012 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2013 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2015 When in doubt, return 0. */
2017 static int
2020 tree other;
2021 {
2033 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2034 and see if the inner values are the same. This removes any
2035 signedness comparison, which doesn't matter here. */
2042 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2043 actual comparison operand, ARG0.
2045 First throw away any conversions to wider types
2046 already present in the operands. */
2055 {
2058 /* Make sure shorter operand is extended the right way
2059 to match the longer operand. */
2065 }
2068 }
2069 \f
2070 /* See if ARG is an expression that is either a comparison or is performing
2071 arithmetic on comparisons. The comparisons must only be comparing
2072 two different values, which will be stored in *CVAL1 and *CVAL2; if
2073 they are nonzero it means that some operands have already been found.
2074 No variables may be used anywhere else in the expression except in the
2075 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2076 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2078 If this is true, return 1. Otherwise, return zero. */
2080 static int
2082 tree arg;
2085 {
2089 /* We can handle some of the 'e' cases here. */
2099 {
2100 /* If we've already found a CVAL1 or CVAL2, this expression is
2101 two complex to handle. */
2107 }
2110 {
2133 /* First see if we can handle the first operand, then the second. For
2134 the second operand, we know *CVAL1 can't be zero. It must be that
2135 one side of the comparison is each of the values; test for the
2136 case where this isn't true by failing if the two operands
2137 are the same. */
2146 ;
2150 ;
2151 else
2155 ;
2159 ;
2160 else
2167 }
2168 }
2169 \f
2170 /* ARG is a tree that is known to contain just arithmetic operations and
2171 comparisons. Evaluate the operations in the tree substituting NEW0 for
2172 any occurrence of OLD0 as an operand of a comparison and likewise for
2173 NEW1 and OLD1. */
2175 static tree
2177 tree arg;
2179 {
2184 /* We can handle some of the 'e' cases here. */
2192 {
2207 {
2224 }
2225 /* fall through - ??? */
2228 {
2232 /* We need to check both for exact equality and tree equality. The
2233 former will be true if the operand has a side-effect. In that
2234 case, we know the operand occurred exactly once. */
2247 }
2251 }
2252 }
2253 \f
2254 /* Return a tree for the case when the result of an expression is RESULT
2255 converted to TYPE and OMITTED was previously an operand of the expression
2256 but is now not needed (e.g., we folded OMITTED * 0).
2258 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2259 the conversion of RESULT to TYPE. */
2261 tree
2264 {
2271 }
2273 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2275 static tree
2278 {
2285 }
2286 \f
2287 /* Return a simplified tree node for the truth-negation of ARG. This
2288 never alters ARG itself. We assume that ARG is an operation that
2289 returns a truth value (0 or 1). */
2291 tree
2293 tree arg;
2294 {
2301 /* If this is a comparison, we can simply invert it, except for
2302 floating-point non-equality comparisons, in which case we just
2303 enclose a TRUTH_NOT_EXPR around what we have. */
2306 {
2308 && !flag_unsafe_math_optimizations
2312 else
2315 }
2318 {
2333 /* Here we can invert either operand. We invert the first operand
2334 unless the second operand is a TRUTH_NOT_EXPR in which case our
2335 result is the XOR of the first operand with the inside of the
2336 negation of the second operand. */
2341 else
2396 }
2400 }
2402 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2403 operands are another bit-wise operation with a common input. If so,
2404 distribute the bit operations to save an operation and possibly two if
2405 constants are involved. For example, convert
2406 (A | B) & (A | C) into A | (B & C)
2407 Further simplification will occur if B and C are constants.
2409 If this optimization cannot be done, 0 will be returned. */
2411 static tree
2414 tree type;
2416 {
2417 tree common;
2427 {
2431 }
2433 {
2437 }
2439 {
2443 }
2445 {
2449 }
2450 else
2455 }
2456 \f
2457 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2458 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
2460 static tree
2462 tree inner;
2463 tree type;
2466 {
2473 }
2475 /* Optimize a bit-field compare.
2477 There are two cases: First is a compare against a constant and the
2478 second is a comparison of two items where the fields are at the same
2479 bit position relative to the start of a chunk (byte, halfword, word)
2480 large enough to contain it. In these cases we can avoid the shift
2481 implicit in bitfield extractions.
2483 For constants, we emit a compare of the shifted constant with the
2484 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2485 compared. For two fields at the same position, we do the ANDs with the
2486 similar mask and compare the result of the ANDs.
2488 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2489 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2490 are the left and right operands of the comparison, respectively.
2492 If the optimization described above can be done, we return the resulting
2493 tree. Otherwise we return zero. */
2495 static tree
2498 tree compare_type;
2500 {
2509 tree mask;
2510 tree offset;
2512 /* Get all the information about the extractions being done. If the bit size
2513 if the same as the size of the underlying object, we aren't doing an
2514 extraction at all and so can do nothing. We also don't want to
2515 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2516 then will no longer be able to replace it. */
2524 {
2525 /* If this is not a constant, we can only do something if bit positions,
2526 sizes, and signedness are the same. */
2534 }
2536 /* See if we can find a mode to refer to this field. We should be able to,
2537 but fail if we can't. */
2546 /* Set signed and unsigned types of the precision of this mode for the
2547 shifts below. */
2551 /* Compute the bit position and size for the new reference and our offset
2552 within it. If the new reference is the same size as the original, we
2553 won't optimize anything, so return zero. */
2563 /* Make the mask to be used against the extracted field. */
2573 /* If not comparing with constant, just rework the comparison
2574 and return. */
2579 mask),
2583 mask));
2585 /* Otherwise, we are handling the constant case. See if the constant is too
2586 big for the field. Warn and return a tree of for 0 (false) if so. We do
2587 this not only for its own sake, but to avoid having to test for this
2588 error case below. If we didn't, we might generate wrong code.
2590 For unsigned fields, the constant shifted right by the field length should
2591 be all zero. For signed fields, the high-order bits should agree with
2592 the sign bit. */
2595 {
2599 {
2605 }
2606 }
2607 else
2608 {
2612 {
2618 }
2619 }
2621 /* Single-bit compares should always be against zero. */
2623 {
2626 }
2628 /* Make a new bitfield reference, shift the constant over the
2629 appropriate number of bits and mask it with the computed mask
2630 (in case this was a signed field). If we changed it, make a new one. */
2633 {
2636 }
2646 rhs);
2647 }
2648 \f
2649 /* Subroutine for fold_truthop: decode a field reference.
2651 If EXP is a comparison reference, we return the innermost reference.
2653 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
2654 set to the starting bit number.
2656 If the innermost field can be completely contained in a mode-sized
2657 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
2659 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
2660 otherwise it is not changed.
2662 *PUNSIGNEDP is set to the signedness of the field.
2664 *PMASK is set to the mask used. This is either contained in a
2665 BIT_AND_EXPR or derived from the width of the field.
2667 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
2669 Return 0 if this is not a component reference or is one that we can't
2670 do anything with. */
2672 static tree
2675 tree exp;
2681 {
2684 tree unsigned_type;
2687 /* All the optimizations using this function assume integer fields.
2688 There are problems with FP fields since the type_for_size call
2689 below can fail for, e.g., XFmode. */
2696 {
2702 }
2711 /* Compute the mask to access the bitfield. */
2721 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
2729 }
2731 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
2732 bit positions. */
2734 static int
2736 tree mask;
2738 {
2741 tree tmask;
2746 return
2753 }
2755 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
2756 represents the sign bit of EXP's type. If EXP represents a sign
2757 or zero extension, also test VAL against the unextended type.
2758 The return value is the (sub)expression whose sign bit is VAL,
2759 or NULL_TREE otherwise. */
2761 static tree
2763 tree exp;
2764 tree val;
2765 {
2767 HOST_WIDE_INT hi;
2769 tree t;
2771 /* Tree EXP must have an integral type. */
2776 /* Tree VAL must be an integer constant. */
2783 {
2786 }
2787 else
2788 {
2791 }
2796 /* Handle extension from a narrower type. */
2802 }
2804 /* Subroutine for fold_truthop: determine if an operand is simple enough
2805 to be evaluated unconditionally. */
2807 static int
2809 tree exp;
2810 {
2811 /* Strip any conversions that don't change the machine mode. */
2823 /* Don't regard global variables as simple. They may be
2824 allocated in ways unknown to the compiler (shared memory,
2825 #pragma weak, etc). */
2828 /* Loading a static variable is unduly expensive, but global
2829 registers aren't expensive. */
2831 }
2832 \f
2833 /* The following functions are subroutines to fold_range_test and allow it to
2834 try to change a logical combination of comparisons into a range test.
2836 For example, both
2837 X == 2 || X == 3 || X == 4 || X == 5
2838 and
2839 X >= 2 && X <= 5
2840 are converted to
2841 (unsigned) (X - 2) <= 3
2843 We describe each set of comparisons as being either inside or outside
2844 a range, using a variable named like IN_P, and then describe the
2845 range with a lower and upper bound. If one of the bounds is omitted,
2846 it represents either the highest or lowest value of the type.
2848 In the comments below, we represent a range by two numbers in brackets
2849 preceded by a "+" to designate being inside that range, or a "-" to
2850 designate being outside that range, so the condition can be inverted by
2851 flipping the prefix. An omitted bound is represented by a "-". For
2852 example, "- [-, 10]" means being outside the range starting at the lowest
2853 possible value and ending at 10, in other words, being greater than 10.
2854 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
2855 always false.
2857 We set up things so that the missing bounds are handled in a consistent
2858 manner so neither a missing bound nor "true" and "false" need to be
2859 handled using a special case. */
2861 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
2862 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
2863 and UPPER1_P are nonzero if the respective argument is an upper bound
2864 and zero for a lower. TYPE, if nonzero, is the type of the result; it
2865 must be specified for a comparison. ARG1 will be converted to ARG0's
2866 type if both are specified. */
2868 static tree
2871 tree type;
2874 {
2875 tree tem;
2879 /* If neither arg represents infinity, do the normal operation.
2880 Else, if not a comparison, return infinity. Else handle the special
2881 comparison rules. Note that most of the cases below won't occur, but
2882 are handled for consistency. */
2885 {
2890 }
2895 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
2896 for neither. In real maths, we cannot assume open ended ranges are
2897 the same. But, this is computer arithmetic, where numbers are finite.
2898 We can therefore make the transformation of any unbounded range with
2899 the value Z, Z being greater than any representable number. This permits
2900 us to treat unbounded ranges as equal. */
2904 {
2925 }
2928 }
2929 \f
2930 /* Given EXP, a logical expression, set the range it is testing into
2931 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
2932 actually being tested. *PLOW and *PHIGH will be made of the same type
2933 as the returned expression. If EXP is not a comparison, we will most
2934 likely not be returning a useful value and range. */
2936 static tree
2938 tree exp;
2941 {
2948 /* Start with simply saying "EXP != 0" and then look at the code of EXP
2949 and see if we can refine the range. Some of the cases below may not
2950 happen, but it doesn't seem worth worrying about this. We "continue"
2951 the outer loop when we've changed something; otherwise we "break"
2952 the switch, which will "break" the while. */
2957 {
2961 {
2972 }
2974 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
2975 lose a cast by accident. */
2980 {
2987 /* We can only do something if the range is testing for zero
2988 and if the second operand is an integer constant. Note that
2989 saying something is "in" the range we make is done by
2990 complementing IN_P since it will set in the initial case of
2991 being not equal to zero; "out" is leaving it alone. */
2998 {
3019 }
3023 /* If this is an unsigned comparison, we also know that EXP is
3024 greater than or equal to zero. We base the range tests we make
3025 on that fact, so we record it here so we can parse existing
3026 range tests. */
3028 {
3031 NULL_TREE))
3036 /* If the high bound is missing, but we
3037 have a low bound, reverse the range so
3038 it goes from zero to the low bound minus 1. */
3040 {
3045 }
3046 }
3050 /* (-x) IN [a,b] -> x in [-b, -a] */
3060 /* ~ X -> -X - 1 */
3069 /* If EXP is signed, any overflow in the computation is undefined,
3070 so we don't worry about it so long as our computations on
3071 the bounds don't overflow. For unsigned, overflow is defined
3072 and this is exactly the right thing. */
3081 /* Check for an unsigned range which has wrapped around the maximum
3082 value thus making n_high < n_low, and normalize it. */
3084 {
3090 /* If the range is of the form +/- [ x+1, x ], we won't
3091 be able to normalize it. But then, it represents the
3092 whole range or the empty set, so make it
3093 +/- [ -, - ]. */
3097 else
3099 }
3100 else
3123 /* If we're converting from an unsigned to a signed type,
3124 we will be doing the comparison as unsigned. The tests above
3125 have already verified that LOW and HIGH are both positive.
3127 So we have to make sure that the original unsigned value will
3128 be interpreted as positive. */
3130 {
3133 tree high_positive;
3135 /* A range without an upper bound is, naturally, unbounded.
3136 Since convert would have cropped a very large value, use
3137 the max value for the destination type. */
3138 high_positive
3147 /* If the low bound is specified, "and" the range with the
3148 range for which the original unsigned value will be
3149 positive. */
3151 {
3155 high_positive))
3159 }
3160 else
3161 {
3162 /* Otherwise, "or" the range with the range of the input
3163 that will be interpreted as negative. */
3167 high_positive))
3171 }
3172 }
3180 }
3183 }
3185 /* If EXP is a constant, we can evaluate whether this is true or false. */
3187 {
3194 }
3198 }
3199 \f
3200 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3201 type, TYPE, return an expression to test if EXP is in (or out of, depending
3202 on IN_P) the range. */
3204 static tree
3206 tree type;
3207 tree exp;
3210 {
3212 tree value;
3231 {
3233 {
3237 }
3239 }
3241 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
3243 {
3245 HOST_WIDE_INT hi;
3250 {
3253 }
3254 else
3255 {
3258 }
3261 {
3263 {
3266 }
3269 }
3270 }
3279 }
3280 \f
3281 /* Given two ranges, see if we can merge them into one. Return 1 if we
3282 can, 0 if we can't. Set the output range into the specified parameters. */
3284 static int
3290 {
3294 tree tem;
3304 /* Make range 0 be the range that starts first, or ends last if they
3305 start at the same value. Swap them if it isn't. */
3308 || (lowequal
3311 {
3315 }
3317 /* Now flag two cases, whether the ranges are disjoint or whether the
3318 second range is totally subsumed in the first. Note that the tests
3319 below are simplified by the ones above. */
3325 /* We now have four cases, depending on whether we are including or
3326 excluding the two ranges. */
3328 {
3329 /* If they don't overlap, the result is false. If the second range
3330 is a subset it is the result. Otherwise, the range is from the start
3331 of the second to the end of the first. */
3336 else
3338 }
3341 {
3342 /* If they don't overlap, the result is the first range. If they are
3343 equal, the result is false. If the second range is a subset of the
3344 first, and the ranges begin at the same place, we go from just after
3345 the end of the first range to the end of the second. If the second
3346 range is not a subset of the first, or if it is a subset and both
3347 ranges end at the same place, the range starts at the start of the
3348 first range and ends just before the second range.
3349 Otherwise, we can't describe this as a single range. */
3355 {
3359 }
3361 {
3365 }
3366 else
3368 }
3371 {
3372 /* If they don't overlap, the result is the second range. If the second
3373 is a subset of the first, the result is false. Otherwise,
3374 the range starts just after the first range and ends at the
3375 end of the second. */
3380 else
3381 {
3385 }
3386 }
3388 else
3389 {
3390 /* The case where we are excluding both ranges. Here the complex case
3391 is if they don't overlap. In that case, the only time we have a
3392 range is if they are adjacent. If the second is a subset of the
3393 first, the result is the first. Otherwise, the range to exclude
3394 starts at the beginning of the first range and ends at the end of the
3395 second. */
3397 {
3404 else
3406 }
3409 else
3411 }
3415 }
3416 \f
3417 #ifndef RANGE_TEST_NON_SHORT_CIRCUIT
3418 #define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
3419 #endif
3421 /* EXP is some logical combination of boolean tests. See if we can
3422 merge it into some range test. Return the new tree if so. */
3424 static tree
3426 tree exp;
3427 {
3434 tree tem;
3436 /* If this is an OR operation, invert both sides; we will invert
3437 again at the end. */
3441 /* If both expressions are the same, if we can merge the ranges, and we
3442 can build the range test, return it or it inverted. If one of the
3443 ranges is always true or always false, consider it to be the same
3444 expression as the other. */
3454 /* On machines where the branch cost is expensive, if this is a
3455 short-circuited branch and the underlying object on both sides
3456 is the same, make a non-short-circuit operation. */
3462 {
3463 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3464 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3465 which cases we can't do this. */
3474 {
3486 }
3487 }
3490 }
3491 \f
3492 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3493 bit value. Arrange things so the extra bits will be set to zero if and
3494 only if C is signed-extended to its full width. If MASK is nonzero,
3495 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3497 static tree
3499 tree c;
3502 tree mask;
3503 {
3506 tree temp;
3511 /* We work by getting just the sign bit into the low-order bit, then
3512 into the high-order bit, then sign-extend. We then XOR that value
3513 with C. */
3517 /* We must use a signed type in order to get an arithmetic right shift.
3518 However, we must also avoid introducing accidental overflows, so that
3519 a subsequent call to integer_zerop will work. Hence we must
3520 do the type conversion here. At this point, the constant is either
3521 zero or one, and the conversion to a signed type can never overflow.
3522 We could get an overflow if this conversion is done anywhere else. */
3530 /* If necessary, convert the type back to match the type of C. */
3535 }
3536 \f
3537 /* Find ways of folding logical expressions of LHS and RHS:
3538 Try to merge two comparisons to the same innermost item.
3539 Look for range tests like "ch >= '0' && ch <= '9'".
3540 Look for combinations of simple terms on machines with expensive branches
3541 and evaluate the RHS unconditionally.
3543 For example, if we have p->a == 2 && p->b == 4 and we can make an
3544 object large enough to span both A and B, we can do this with a comparison
3545 against the object ANDed with the a mask.
3547 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3548 operations to do this with one comparison.
3550 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3551 function and the one above.
3553 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3554 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3556 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3557 two operands.
3559 We return the simplified tree or 0 if no optimization is possible. */
3561 static tree
3565 {
3566 /* If this is the "or" of two comparisons, we can do something if
3567 the comparisons are NE_EXPR. If this is the "and", we can do something
3568 if the comparisons are EQ_EXPR. I.e.,
3569 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3571 WANTED_CODE is this operation code. For single bit fields, we can
3572 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3573 comparison for one-bit fields. */
3593 /* Start by getting the comparison codes. Fail if anything is volatile.
3594 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3595 it were surrounded with a NE_EXPR. */
3620 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
3624 {
3629 {
3637 }
3640 {
3649 }
3650 else
3660 }
3662 /* If the RHS can be evaluated unconditionally and its operands are
3663 simple, it wins to evaluate the RHS unconditionally on machines
3664 with expensive branches. In this case, this isn't a comparison
3665 that can be merged. Avoid doing this if the RHS is a floating-point
3666 comparison since those can trap. */
3672 {
3673 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
3681 integer_zero_node);
3683 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
3691 integer_zero_node);
3694 }
3696 /* See if the comparisons can be merged. Then get all the parameters for
3697 each side. */
3721 /* It must be true that the inner operation on the lhs of each
3722 comparison must be the same if we are to be able to do anything.
3723 Then see if we have constants. If not, the same must be true for
3724 the rhs's. */
3735 else
3738 /* If either comparison code is not correct for our logical operation,
3739 fail. However, we can convert a one-bit comparison against zero into
3740 the opposite comparison against that bit being set in the field. */
3744 {
3746 {
3747 /* Make the left operand unsigned, since we are only interested
3748 in the value of one bit. Otherwise we are doing the wrong
3749 thing below. */
3752 }
3753 else
3755 }
3757 /* This is analogous to the code for l_const above. */
3759 {
3761 {
3764 }
3765 else
3767 }
3769 /* After this point all optimizations will generate bit-field
3770 references, which we might not want. */
3774 /* See if we can find a mode that contains both fields being compared on
3775 the left. If we can't, fail. Otherwise, update all constants and masks
3776 to be relative to a field of that size. */
3781 volatilep);
3791 {
3794 }
3802 {
3810 {
3814 wanted_code == NE_EXPR
3816 }
3817 }
3819 {
3827 {
3831 wanted_code == NE_EXPR
3833 }
3834 }
3836 /* If the right sides are not constant, do the same for it. Also,
3837 disallow this optimization if a size or signedness mismatch occurs
3838 between the left and right sides. */
3840 {
3843 /* Make sure the two fields on the right
3844 correspond to the left without being swapped. */
3852 volatilep);
3862 {
3865 }
3872 /* Make a mask that corresponds to both fields being compared.
3873 Do this for both items being compared. If the operands are the
3874 same size and the bits being compared are in the same position
3875 then we can do this by masking both and comparing the masked
3876 results. */
3880 {
3892 }
3894 /* There is still another way we can do something: If both pairs of
3895 fields being compared are adjacent, we may be able to make a wider
3896 field containing them both.
3898 Note that we still must mask the lhs/rhs expressions. Furthermore,
3899 the mask must be shifted to account for the shift done by
3900 make_bit_field_ref. */
3905 {
3906 tree type;
3918 /* Convert to the smaller type before masking out unwanted bits. */
3921 {
3923 {
3927 }
3929 {
3933 }
3934 }
3943 }
3946 }
3948 /* Handle the case of comparisons with constants. If there is something in
3949 common between the masks, those bits of the constants must be the same.
3950 If not, the condition is always false. Test for this to avoid generating
3951 incorrect code below. */
3956 {
3958 {
3961 }
3962 else
3963 {
3966 }
3967 }
3969 /* Construct the expression we will return. First get the component
3970 reference we will make. Unless the mask is all ones the width of
3971 that field, perform the mask operation. Then compare with the
3972 merged constant. */
3982 }
3983 \f
3984 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
3985 constant. */
3987 static tree
3989 tree t;
3990 {
3995 tree minmax_const;
3997 tree inner;
4007 /* If something does not permit us to optimize, return the original tree. */
4015 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4016 and GT_EXPR, doing the rest with recursive calls using logical
4017 simplifications. */
4019 {
4021 return
4025 return
4027 optimize_minmax_comparison
4029 optimize_minmax_comparison
4034 /* MAX (X, 0) == 0 -> X <= 0 */
4038 /* MAX (X, 0) == 5 -> X == 5 */
4042 /* MAX (X, 0) == -1 -> false */
4046 /* MIN (X, 0) == 0 -> X >= 0 */
4050 /* MIN (X, 0) == 5 -> false */
4053 else
4054 /* MIN (X, 0) == -1 -> X == -1 */
4059 /* MAX (X, 0) > 0 -> X > 0
4060 MAX (X, 0) > 5 -> X > 5 */
4064 /* MAX (X, 0) > -1 -> true */
4068 /* MIN (X, 0) > 0 -> false
4069 MIN (X, 0) > 5 -> false */
4072 else
4073 /* MIN (X, 0) > -1 -> X > -1 */
4078 }
4079 }
4080 \f
4081 /* T is an integer expression that is being multiplied, divided, or taken a
4082 modulus (CODE says which and what kind of divide or modulus) by a
4083 constant C. See if we can eliminate that operation by folding it with
4084 other operations already in T. WIDE_TYPE, if non-null, is a type that
4085 should be used for the computation if wider than our type.
4087 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
4088 (X * 2) + (Y * 4). We must, however, be assured that either the original
4089 expression would not overflow or that overflow is undefined for the type
4090 in the language in question.
4092 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4093 the machine has a multiply-accumulate insn or that this is part of an
4094 addressing calculation.
4096 If we return a non-null expression, it is an equivalent form of the
4097 original computation, but need not be in the original type. */
4099 static tree
4101 tree t;
4102 tree c;
4104 tree wide_type;
4105 {
4106 /* To avoid exponential search depth, refuse to allow recursion past
4107 three levels. Beyond that (1) it's highly unlikely that we'll find
4108 something interesting and (2) we've probably processed it before
4109 when we built the inner expression. */
4112 tree ret;
4117 depth++;
4119 depth--;
4122 }
4124 static tree
4126 tree t;
4127 tree c;
4129 tree wide_type;
4130 {
4140 /* Don't deal with constants of zero here; they confuse the code below. */
4150 /* Note that we need not handle conditional operations here since fold
4151 already handles those cases. So just do arithmetic here. */
4153 {
4155 /* For a constant, we can always simplify if we are a multiply
4156 or (for divide and modulus) if it is a multiple of our constant. */
4163 /* If op0 is an expression ... */
4168 /* ... and is unsigned, and its type is smaller than ctype,
4169 then we cannot pass through as widening. */
4175 /* ... or its type is larger than ctype,
4176 then we cannot pass through this truncation. */
4179 /* ... or signedness changes for division or modulus,
4180 then we cannot pass through this conversion. */
4186 /* Pass the constant down and see if we can make a simplification. If
4187 we can, replace this expression with the inner simplification for
4188 possible later conversion to our or some other type. */
4193 code == MULT_EXPR
4204 /* If widening the type changes the signedness, then we can't perform
4205 this optimization as that changes the result. */
4209 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4212 {
4218 }
4228 /* If this has not been evaluated and the operand has no side effects,
4229 we can see if we can do something inside it and make a new one.
4230 Note that this test is overly conservative since we can do this
4231 if the only reason it had side effects is that it was another
4232 similar SAVE_EXPR, but that isn't worth bothering with. */
4235 wide_type)))
4236 {
4243 }
4247 /* If the second operand is constant, this is a multiplication
4248 or floor division, by a power of two, so we can treat it that
4249 way unless the multiplier or divisor overflows. */
4251 /* const_binop may not detect overflow correctly,
4252 so check for it explicitly here. */
4266 /* See if we can eliminate the operation on both sides. If we can, we
4267 can return a new PLUS or MINUS. If we can't, the only remaining
4268 cases where we can do anything are if the second operand is a
4269 constant. */
4274 /* If not multiplication, we can only do this if both operands
4275 are divisible by c. */
4281 /* If this was a subtraction, negate OP1 and set it to be an addition.
4282 This simplifies the logic below. */
4289 /* If either OP1 or C are negative, this optimization is not safe for
4290 some of the division and remainder types while for others we need
4291 to change the code. */
4293 {
4301 }
4303 /* If it's a multiply or a division/modulus operation of a multiple
4304 of our constant, do the operation and verify it doesn't overflow. */
4307 {
4311 }
4312 else
4315 /* If we have an unsigned type is not a sizetype, we cannot widen
4316 the operation since it will change the result if the original
4317 computation overflowed. */
4323 /* If we were able to eliminate our operation from the first side,
4324 apply our operation to the second side and reform the PLUS. */
4328 /* The last case is if we are a multiply. In that case, we can
4329 apply the distributive law to commute the multiply and addition
4330 if the multiplication of the constants doesn't overflow. */
4335 op1));
4340 /* We have a special case here if we are doing something like
4341 (C * 8) % 4 since we know that's zero. */
4348 /* ... fall through ... */
4352 /* If we can extract our operation from the LHS, do so and return a
4353 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4354 do something only if the second operand is a constant. */
4366 /* If these are the same operation types, we can associate them
4367 assuming no overflow. */
4374 /* If these operations "cancel" each other, we have the main
4375 optimizations of this pass, which occur when either constant is a
4376 multiple of the other, in which case we replace this with either an
4377 operation or CODE or TCODE.
4379 If we have an unsigned type that is not a sizetype, we cannot do
4380 this since it will change the result if the original computation
4381 overflowed. */
4388 {
4399 }
4404 }
4407 }
4408 \f
4409 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4410 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4411 that we may sometimes modify the tree. */
4413 static tree
4415 tree t;
4416 tree s;
4417 {
4420 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4425 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4426 don't bother handling any other types. */
4428 {
4432 }
4437 {
4440 }
4443 }
4444 \f
4445 /* Return a node which has the indicated constant VALUE (either 0 or
4446 1), and is of the indicated TYPE. */
4448 static tree
4451 tree type;
4452 {
4457 integer_zero_node);
4458 else
4459 {
4464 }
4465 }
4467 /* Utility function for the following routine, to see how complex a nesting of
4468 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4469 we don't care (to avoid spending too much time on complex expressions.). */
4471 static int
4473 tree expr;
4475 {
4486 }
4488 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
4489 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4490 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4491 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
4492 COND is the first argument to CODE; otherwise (as in the example
4493 given here), it is the second argument. TYPE is the type of the
4494 original expression. */
4496 static tree
4499 tree type;
4500 tree cond;
4501 tree arg;
4503 {
4507 /* In the end, we'll produce a COND_EXPR. Both arms of the
4508 conditional expression will be binary operations. The left-hand
4509 side of the expression to be executed if the condition is true
4510 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4511 of the expression to be executed if the condition is true will be
4512 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analogous --
4513 but apply to the expression to be executed if the conditional is
4514 false. */
4519 /* These are the codes to use for the left-hand side and right-hand
4520 side of the COND_EXPR. Normally, they are the same as CODE. */
4523 /* And these are the types of the expressions. */
4529 {
4533 }
4534 else
4535 {
4539 }
4542 {
4546 /* If this operand throws an expression, then it does not make
4547 sense to try to perform a logical or arithmetic operation
4548 involving it. Instead of building `a + throw 3' for example,
4549 we simply build `a, throw 3'. */
4551 {
4553 {
4556 }
4557 else
4559 }
4561 {
4563 {
4566 }
4567 else
4569 }
4570 }
4571 else
4572 {
4577 }
4579 /* If ARG is complex we want to make sure we only evaluate it once. Though
4580 this is only required if it is volatile, it might be more efficient even
4581 if it is not. However, if we succeed in folding one part to a constant,
4582 we do not need to make this SAVE_EXPR. Since we do this optimization
4583 primarily to see if we do end up with constant and this SAVE_EXPR
4584 interferes with later optimizations, suppressing it when we can is
4585 important.
4587 If we are not in a function, we can't make a SAVE_EXPR, so don't try to
4588 do so. Don't try to see if the result is a constant if an arm is a
4589 COND_EXPR since we get exponential behavior in that case. */
4598 {
4607 {
4611 }
4612 }
4625 else
4627 }
4629 \f
4630 /* Subroutine of fold() that checks for the addition of +/- 0.0.
4632 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
4633 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
4634 ADDEND is the same as X.
4636 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
4637 and finite. The problematic cases are when X is zero, and its mode
4638 has signed zeros. In the case of rounding towards -infinity,
4639 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
4640 modes, X + 0 is not the same as X because -0 + 0 is 0. */
4642 static bool
4646 {
4650 /* Don't allow the fold with -fsignaling-nans. */
4654 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
4658 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
4663 /* The mode has signed zeros, and we have to honor their sign.
4664 In this situation, there is only one case we can return true for.
4665 X - 0 is the same as X unless rounding towards -infinity is
4666 supported. */
4668 }
4670 /* Subroutine of fold() that checks comparisons of built-in math
4671 functions against real constants.
4673 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
4674 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
4675 is the type of the result and ARG0 and ARG1 are the operands of the
4676 comparison. ARG1 must be a TREE_REAL_CST.
4678 The function returns the constant folded tree if a simplification
4679 can be made, and NULL_TREE otherwise. */
4681 static tree
4686 {
4687 REAL_VALUE_TYPE c;
4692 {
4698 {
4699 /* sqrt(x) < y is always false, if y is negative. */
4703 arg);
4705 /* sqrt(x) > y is always true, if y is negative and we
4706 don't care about NaNs, i.e. negative values of x. */
4710 arg);
4712 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
4715 }
4717 {
4718 REAL_VALUE_TYPE c2;
4724 {
4725 /* sqrt(x) > y is x == +Inf, when y is very large. */
4730 /* sqrt(x) > y is always false, when y is very large
4731 and we don't care about infinities. */
4734 arg);
4735 }
4737 /* sqrt(x) > c is the same as x > c*c. */
4740 }
4742 {
4743 REAL_VALUE_TYPE c2;
4749 {
4750 /* sqrt(x) < y is always true, when y is a very large
4751 value and we don't care about NaNs or Infinities. */
4755 arg);
4757 /* sqrt(x) < y is x != +Inf when y is very large and we
4758 don't care about NaNs. */
4763 /* sqrt(x) < y is x >= 0 when y is very large and we
4764 don't care about Infinities. */
4769 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
4778 dconst0))),
4781 c2)))));
4782 }
4784 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
4789 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
4792 {
4797 dconst0))),
4800 c2)))));
4801 }
4802 }
4803 }
4806 }
4808 /* Subroutine of fold() that optimizes comparisons against Infinities,
4809 either +Inf or -Inf.
4811 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
4812 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
4813 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
4815 The function returns the constant folded tree if a simplification
4816 can be made, and NULL_TREE otherwise. */
4818 static tree
4822 {
4823 /* For negative infinity swap the sense of the comparison. */
4828 {
4830 /* x > +Inf is always false, if with ignore sNANs. */
4835 arg0);
4838 /* x <= +Inf is always true, if we don't case about NaNs. */
4842 arg0);
4844 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
4847 {
4850 }
4860 }
4863 }
4865 /* Perform constant folding and related simplification of EXPR.
4866 The related simplifications include x*1 => x, x*0 => 0, etc.,
4867 and application of the associative law.
4868 NOP_EXPR conversions may be removed freely (as long as we
4869 are careful not to change the C type of the overall expression)
4870 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4871 but we can constant-fold them if they have constant operands. */
4873 tree
4875 tree expr;
4876 {
4879 tree tem;
4885 /* WINS will be nonzero when the switch is done
4886 if all operands are constant. */
4889 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4890 Likewise for a SAVE_EXPR that's already been evaluated. */
4894 /* Return right away if a constant. */
4898 #ifdef MAX_INTEGER_COMPUTATION_MODE
4900 #endif
4903 {
4904 tree subop;
4906 /* Special case for conversion ops that can have fixed point args. */
4909 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4915 else
4920 )
4921 /* Note that TREE_CONSTANT isn't enough:
4922 static var addresses are constant but we can't
4923 do arithmetic on them. */
4925 }
4927 {
4931 {
4933 tree subop;
4939 {
4940 /* Signedness matters here. Perhaps we can refine this
4941 later. */
4943 }
4944 else
4945 /* Strip any conversions that don't change the mode. */
4950 else
4955 /* Note that TREE_CONSTANT isn't enough:
4956 static var addresses are constant but we can't
4957 do arithmetic on them. */
4964 }
4965 }
4967 /* If this is a commutative operation, and ARG0 is a constant, move it
4968 to ARG1 to reduce the number of tests below. */
4973 {
4978 }
4980 /* Now WINS is set as described above,
4981 ARG0 is the first operand of EXPR,
4982 and ARG1 is the second operand (if it has more than one operand).
4984 First check for cases where an arithmetic operation is applied to a
4985 compound, conditional, or comparison operation. Push the arithmetic
4986 operation inside the compound or conditional to see if any folding
4987 can then be done. Convert comparison to conditional for this purpose.
4988 The also optimizes non-constant cases that used to be done in
4989 expand_expr.
4991 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
4992 one of the operands is a comparison and the other is a comparison, a
4993 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
4994 code below would make the expression more complex. Change it to a
4995 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
4996 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5008 {
5018 }
5021 {
5026 {
5036 /* If this was a conversion, and all we did was to move into
5037 inside the COND_EXPR, bring it back out. But leave it if
5038 it is a conversion from integer to integer and the
5039 result precision is no wider than a word since such a
5040 conversion is cheap and may be optimized away by combine,
5041 while it couldn't if it were outside the COND_EXPR. Then return
5042 so we don't get into an infinite recursion loop taking the
5043 conversion out and then back in. */
5055 && (INTEGRAL_TYPE_P
5066 }
5071 }
5082 {
5097 return
5111 return
5114 }
5117 {
5133 /* Other kinds of FIX are not handled properly by fold_convert. */
5138 /* Handle cases of two conversions in a row. */
5141 {
5161 /* In addition to the cases of two conversions in a row
5162 handled below, if we are converting something to its own
5163 type via an object of identical or wider precision, neither
5164 conversion is needed. */
5170 /* Likewise, if the intermediate and final types are either both
5171 float or both integer, we don't need the middle conversion if
5172 it is wider than the final type and doesn't change the signedness
5173 (for integers). Avoid this if the final type is a pointer
5174 since then we sometimes need the inner conversion. Likewise if
5175 the outer has a precision not equal to the size of its mode. */
5185 /* If we have a sign-extension of a zero-extended value, we can
5186 replace that by a single zero-extension. */
5192 /* Two conversions in a row are not needed unless:
5193 - some conversion is floating-point (overstrict for now), or
5194 - the intermediate type is narrower than both initial and
5195 final, or
5196 - the intermediate type and innermost type differ in signedness,
5197 and the outermost type is wider than the intermediate, or
5198 - the initial type is a pointer type and the precisions of the
5199 intermediate and final types differ, or
5200 - the final type is a pointer type and the precisions of the
5201 initial and intermediate types differ. */
5215 }
5219 /* Detect assigning a bitfield. */
5222 {
5223 /* Don't leave an assignment inside a conversion
5224 unless assigning a bitfield. */
5227 /* First do the assignment, then return converted constant. */
5231 }
5233 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
5234 constants (if x has signed type, the sign bit cannot be set
5235 in c). This folds extension into the BIT_AND_EXPR. */
5240 {
5250 <= HOST_BITS_PER_WIDE_INT
5252 {
5259 #ifdef LOAD_EXTEND_OP
5263 {
5267 }
5268 #endif
5269 }
5274 }
5277 {
5280 }
5291 {
5295 }
5304 {
5306 {
5308 HOST_WIDE_INT high;
5319 }
5322 }
5325 /* Convert -((double)float) into (double)(-float). */
5328 {
5333 }
5335 /* Convert - (a - b) to (b - a) for non-floating-point. */
5345 {
5347 {
5348 /* If the value is unsigned, then the absolute value is
5349 the same as the ordinary value. */
5352 /* Similarly, if the value is non-negative. */
5355 /* If the value is negative, then the absolute value is
5356 its negation. */
5357 else
5358 {
5360 HOST_WIDE_INT high;
5371 }
5372 }
5374 {
5378 }
5379 }
5382 /* Convert fabs((double)float) into (double)fabsf(float). */
5385 {
5390 }
5391 else
5392 {
5393 /* fabs(sqrt(x)) = sqrt(x) and fabs(exp(x)) = exp(x). */
5402 }
5427 {
5434 }
5440 /* A + (-B) -> A - B */
5443 /* (-A) + B -> B - A */
5447 {
5451 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5452 with a constant, and the two constants have no bits in common,
5453 we should treat this as a BIT_IOR_EXPR since this may produce more
5454 simplifications. */
5462 {
5465 }
5467 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5468 (plus (plus (mult) (mult)) (foo)) so that we can
5469 take advantage of the factoring cases below. */
5474 {
5479 else
5500 }
5503 {
5507 /* (A * C) + (B * C) -> (A+B) * C.
5508 We are most concerned about the case where C is a constant,
5509 but other combinations show up during loop reduction. Since
5510 it is not difficult, try all four possibilities. */
5527 /* No identical multiplicands; see if we can find a common
5528 power-of-two factor in non-power-of-two multiplies. This
5529 can help in multi-dimensional array access. */
5534 {
5539 /* Move min of absolute values to int11. */
5542 {
5546 }
5549 {
5554 }
5555 }
5560 same));
5561 }
5562 }
5564 /* See if ARG1 is zero and X + ARG1 reduces to X. */
5568 /* Likewise if the operands are reversed. */
5572 bit_rotate:
5573 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5574 is a rotate of A by C1 bits. */
5575 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5576 is a rotate of A by B bits. */
5577 {
5586 {
5605 {
5613 TYPE_PRECISION
5618 ? LROTATE_EXPR
5621 }
5623 {
5631 TYPE_PRECISION
5636 ? LROTATE_EXPR
5639 }
5640 }
5641 }
5643 associate:
5644 /* In most languages, can't associate operations on floats through
5645 parentheses. Rather than remember where the parentheses were, we
5646 don't associate floats at all. It shouldn't matter much. However,
5647 associating multiplications is only very slightly inaccurate, so do
5648 that if -funsafe-math-optimizations is specified. */
5653 {
5657 /* Split both trees into variables, constants, and literals. Then
5658 associate each group together, the constants with literals,
5659 then the result with variables. This increases the chances of
5660 literals being recombined later and of generating relocatable
5661 expressions for the sum of a constant and literal. */
5666 /* Only do something if we found more than two objects. Otherwise,
5667 nothing has changed and we risk infinite recursion. */
5672 {
5673 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
5682 /* Preserve the MINUS_EXPR if the negative part of the literal is
5683 greater than the positive part. Otherwise, the multiplicative
5684 folding code (i.e extract_muldiv) may be fooled in case
5685 unsigned constants are substracted, like in the following
5686 example: ((X*2 + 4) - 8U)/2. */
5688 {
5690 {
5694 }
5695 else
5696 {
5700 }
5701 }
5703 {
5707 else
5708 {
5713 }
5714 }
5718 }
5719 }
5721 binary:
5725 {
5726 /* The return value should always have
5727 the same type as the original expression. */
5732 }
5736 /* A - (-B) -> A + B */
5739 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
5749 {
5755 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5756 about the case where C is a constant, just try one of the
5757 four possibilities. */
5768 /* Fold A - (A & B) into ~B & A. */
5771 {
5776 arg0));
5781 arg0));
5782 }
5783 }
5785 /* See if ARG1 is zero and X - ARG1 reduces to X. */
5789 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
5790 ARG0 is zero and X + ARG0 reduces to X, since that would mean
5791 (-ARG1 + ARG0) reduces to -ARG1. */
5795 /* Fold &x - &x. This can happen from &x.foo - &x.
5796 This is unsafe for certain floats even in non-IEEE formats.
5797 In IEEE, it is unsafe because it does wrong for NaNs.
5798 Also note that operand_equal_p is always false if an operand
5799 is volatile. */
5808 /* (-A) * (-B) -> A * B */
5814 {
5820 /* (a * (1 << b)) is (a << b) */
5836 }
5837 else
5838 {
5839 /* Maybe fold x * 0 to 0. The expressions aren't the same
5840 when x is NaN, since x * 0 is also NaN. Nor are they the
5841 same in modes with signed zeros, since multiplying a
5842 negative value by 0 gives -0, not +0. */
5847 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
5852 /* Transform x * -1.0 into -x. */
5857 /* x*2 is x+x */
5861 {
5864 }
5867 {
5871 /* Optimizations of sqrt(...)*sqrt(...). */
5875 {
5880 /* Optimize sqrt(x)*sqrt(x) as x. */
5885 /* Optimize sqrt(x)*sqrt(y) as sqrt(x*y). */
5890 }
5892 /* Optimize exp(x)*exp(y) as exp(x+y). */
5896 {
5903 }
5905 /* Optimizations of pow(...)*pow(...). */
5909 {
5917 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
5919 {
5924 arg01));
5926 }
5928 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
5930 {
5935 arg));
5937 }
5938 }
5939 }
5940 }
5944 bit_ior:
5953 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
5955 This results in more efficient code for machines without a NAND
5956 instruction. Combine will canonicalize to the first form
5957 which will allow use of NAND instructions provided by the
5958 backend if they exist. */
5961 {
5966 }
5968 /* See if this can be simplified into a rotate first. If that
5969 is unsuccessful continue in the association code. */
5978 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
5979 with a constant, and the two constants have no bits in common,
5980 we should treat this as a BIT_IOR_EXPR since this may produce more
5981 simplifications. */
5989 {
5992 }
5994 /* See if this can be simplified into a rotate first. If that
5995 is unsuccessful continue in the association code. */
5999 bit_and:
6007 /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char. */
6010 {
6011 unsigned int prec
6018 }
6020 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
6022 This results in more efficient code for machines without a NOR
6023 instruction. Combine will canonicalize to the first form
6024 which will allow use of NOR instructions provided by the
6025 backend if they exist. */
6028 {
6033 }
6043 {
6047 }
6051 /* Don't touch a floating-point divide by zero unless the mode
6052 of the constant can represent infinity. */
6058 /* (-A) / (-B) -> A / B */
6063 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
6068 /* If ARG1 is a constant, we can convert this to a multiply by the
6069 reciprocal. This does not have the same rounding properties,
6070 so only do this if -funsafe-math-optimizations. We can actually
6071 always safely do it if ARG1 is a power of two, but it's hard to
6072 tell if it is or not in a portable manner. */
6074 {
6079 /* Find the reciprocal if optimizing and the result is exact. */
6081 {
6082 REAL_VALUE_TYPE r;
6085 {
6088 }
6089 }
6090 }
6091 /* Convert A/B/C to A/(B*C). */
6094 {
6097 arg1)));
6098 }
6099 /* Convert A/(B/C) to (A/B)*C. */
6102 {
6107 }
6110 {
6112 /* Optimize x/exp(y) into x*exp(-y). */
6116 {
6123 }
6125 /* Optimize x/pow(y,z) into x*pow(y,-z). */
6129 {
6138 }
6139 }
6152 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
6153 operation, EXACT_DIV_EXPR.
6155 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
6156 At one time others generated faster code, it's not clear if they do
6157 after the last round to changes to the DIV code in expmed.c. */
6192 /* Optimize -1 >> x for arithmetic right shifts. */
6195 /* ... fall through ... */
6198 shift:
6204 /* Since negative shift count is not well-defined,
6205 don't try to compute it in the compiler. */
6208 /* Rewrite an LROTATE_EXPR by a constant into an
6209 RROTATE_EXPR by a new constant. */
6211 {
6215 = const_binop
6222 }
6224 /* If we have a rotate of a bit operation with the rotate count and
6225 the second operand of the bit operation both constant,
6226 permute the two operations. */
6239 /* Two consecutive rotates adding up to the width of the mode can
6240 be ignored. */
6271 /* Note that the operand of this must be an int
6272 and its values must be 0 or 1.
6273 ("true" is a fixed value perhaps depending on the language,
6274 but we don't handle values other than 1 correctly yet.) */
6276 /* Avoid infinite recursion. */
6282 /* Note that the operands of this must be ints
6283 and their values must be 0 or 1.
6284 ("true" is a fixed value perhaps depending on the language.) */
6285 /* If first arg is constant zero, return it. */
6289 /* If either arg is constant true, drop it. */
6293 /* Preserve sequence points. */
6296 /* If second arg is constant zero, result is zero, but first arg
6297 must be evaluated. */
6300 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
6301 case will be handled here. */
6305 truth_andor:
6306 /* We only do these simplifications if we are optimizing. */
6310 /* Check for things like (A || B) && (A || C). We can convert this
6311 to A || (B && C). Note that either operator can be any of the four
6312 truth and/or operations and the transformation will still be
6313 valid. Also note that we only care about order for the
6314 ANDIF and ORIF operators. If B contains side effects, this
6315 might change the truth-value of A. */
6322 {
6342 /* This case if tricky because we must either have commutative
6343 operators or else A10 must not have side-effects. */
6349 a01));
6350 }
6352 /* See if we can build a range comparison. */
6356 /* Check for the possibility of merging component references. If our
6357 lhs is another similar operation, try to merge its rhs with our
6358 rhs. Then try to merge our lhs and rhs. */
6370 /* Note that the operands of this must be ints
6371 and their values must be 0 or true.
6372 ("true" is a fixed value perhaps depending on the language.) */
6373 /* If first arg is constant true, return it. */
6377 /* If either arg is constant zero, drop it. */
6381 /* Preserve sequence points. */
6384 /* If second arg is constant true, result is true, but we must
6385 evaluate first arg. */
6388 /* Likewise for first arg, but note this only occurs here for
6389 TRUTH_OR_EXPR. */
6395 /* If either arg is constant zero, drop it. */
6400 /* If either arg is constant true, this is a logical inversion. */
6413 /* If one arg is a real or integer constant, put it last. */
6418 {
6425 }
6428 {
6436 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
6441 /* (-a) CMP (-b) -> b CMP a */
6448 {
6449 REAL_VALUE_TYPE cst;
6452 /* (-a) CMP CST -> a swap(CMP) (-CST) */
6454 return
6460 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
6461 /* a CMP (-0) -> a CMP 0 */
6466 /* x != NaN is always true, other ops are always false. */
6469 {
6472 }
6474 /* Fold comparisons against infinity. */
6476 {
6480 }
6481 }
6483 /* If this is a comparison of a real constant with a PLUS_EXPR
6484 or a MINUS_EXPR of a real constant, we can convert it into a
6485 comparison with a revised real constant as long as no overflow
6486 occurs when unsafe_math_optimizations are enabled. */
6498 /* Likewise, we can simplify a comparison of a real constant with
6499 a MINUS_EXPR whose first operand is also a real constant, i.e.
6500 (c1 - x) < c2 becomes x > c1-c2. */
6511 /* Fold comparisons against built-in math functions. */
6513 && flag_unsafe_math_optimizations
6515 {
6519 {
6523 }
6524 }
6525 }
6527 /* Convert foo++ == CONST into ++foo == CONST + INCR.
6528 First, see if one arg is constant; find the constant arg
6529 and the other one. */
6530 {
6540 {
6541 /* This optimization is invalid for ordered comparisons
6542 if CONST+INCR overflows or if foo+incr might overflow.
6543 This optimization is invalid for floating point due to rounding.
6544 For pointer types we assume overflow doesn't happen. */
6548 {
6549 tree newconst
6553 /* Do not overwrite the current varop to be a preincrement,
6554 create a new node so that we won't confuse our caller who
6555 might create trees and throw them away, reusing the
6556 arguments that they passed to build. This shows up in
6557 the THEN or ELSE parts of ?: being postincrements. */
6562 /* If VAROP is a reference to a bitfield, we must mask
6563 the constant by the width of the field. */
6567 {
6568 int size
6570 (TREE_OPERAND
6574 tree folded_compare;
6576 /* First check whether the comparison would come out
6577 always the same. If we don't do that we would
6578 change the meaning with the masking. */
6582 else
6585 constop));
6600 mask)));
6601 }
6607 }
6608 }
6610 {
6614 {
6615 tree newconst
6619 /* Do not overwrite the current varop to be a predecrement,
6620 create a new node so that we won't confuse our caller who
6621 might create trees and throw them away, reusing the
6622 arguments that they passed to build. This shows up in
6623 the THEN or ELSE parts of ?: being postdecrements. */
6631 {
6632 int size
6634 (TREE_OPERAND
6638 tree folded_compare;
6643 else
6646 constop));
6661 mask)));
6662 }
6668 }
6669 }
6670 }
6672 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
6673 This transformation affects the cases which are handled in later
6674 optimizations involving comparisons with non-negative constants. */
6678 {
6680 {
6695 }
6696 }
6698 /* Comparisons with the highest or lowest possible integer of
6699 the specified size will have known values. */
6700 {
6708 {
6715 {
6718 }
6719 else
6720 {
6723 }
6728 {
6732 arg0);
6740 arg0);
6746 /* The GE_EXPR and LT_EXPR cases above are not normally
6747 reached because of previous transformations. */
6751 }
6755 {
6768 }
6772 {
6776 arg0);
6785 arg0);
6793 }
6797 {
6810 }
6815 /* signed_type does not work on pointer types. */
6817 {
6818 /* The following case also applies to X < signed_max+1
6819 and X >= signed_max+1 because previous transformations. */
6821 {
6825 return fold
6829 }
6830 }
6831 }
6832 }
6834 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6835 a MINUS_EXPR of a constant, we can convert it into a comparison with
6836 a revised constant as long as no overflow occurs. */
6848 /* Similarly for a NEGATE_EXPR. */
6857 /* If we have X - Y == 0, we can convert that to X == Y and similarly
6858 for !=. Don't do this for ordered comparisons due to overflow. */
6864 /* If we are widening one operand of an integer comparison,
6865 see if the other operand is similarly being widened. Perhaps we
6866 can do the comparison in the narrower type. */
6876 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
6877 constant, we can simplify it. */
6884 /* If we are comparing an ABS_EXPR with a constant, we can
6885 convert all the cases into explicit comparisons, but they may
6886 well not be faster than doing the ABS and one comparison.
6887 But ABS (X) <= C is a range comparison, which becomes a subtraction
6888 and a comparison, and is probably faster. */
6900 /* If this is an EQ or NE comparison with zero and ARG0 is
6901 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
6902 two operations, but the latter can be done in one less insn
6903 on machines that have only two-operand insns or on which a
6904 constant cannot be the first operand. */
6907 {
6910 return
6918 integer_one_node)),
6919 arg1));
6922 return
6930 integer_one_node)),
6931 arg1));
6932 }
6934 /* If this is an NE or EQ comparison of zero against the result of a
6935 signed MOD operation whose second operand is a power of 2, make
6936 the MOD operation unsigned since it is simpler and equivalent. */
6945 {
6952 }
6954 /* If this is an NE comparison of zero with an AND of one, remove the
6955 comparison since the AND will give the correct value. */
6961 /* If we have (A & C) == C where C is a power of 2, convert this into
6962 (A & C) != 0. Similarly for NE_EXPR. */
6970 /* If we have (A & C) != 0 where C is the sign bit of A, convert
6971 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
6975 {
6979 {
6984 }
6985 }
6987 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
6988 and similarly for >= into !=. */
7004 return
7011 /* Simplify comparison of something with itself. (For IEEE
7012 floating-point, we can only do some of these simplifications.) */
7014 {
7016 {
7027 /* For NE, we can only do this simplification if integer. */
7030 /* ... fall through ... */
7036 }
7037 }
7039 /* If we are comparing an expression that just has comparisons
7040 of two integer values, arithmetic expressions of those comparisons,
7041 and constants, we can simplify it. There are only three cases
7042 to check: the two values can either be equal, the first can be
7043 greater, or the second can be greater. Fold the expression for
7044 those three values. Since each value must be 0 or 1, we have
7045 eight possibilities, each of which corresponds to the constant 0
7046 or 1 or one of the six possible comparisons.
7048 This handles common cases like (a > b) == 0 but also handles
7049 expressions like ((x > y) - (y > x)) > 0, which supposedly
7050 occur in macroized code. */
7053 {
7058 /* Don't handle degenerate cases here; they should already
7059 have been handled anyway. */
7068 {
7072 /* We can't just pass T to eval_subst in case cval1 or cval2
7073 was the same as ARG1. */
7075 tree high_result
7078 arg1));
7079 tree equal_result
7082 arg1));
7083 tree low_result
7086 arg1));
7088 /* All three of these results should be 0 or 1. Confirm they
7089 are. Then use those values to select the proper code
7090 to use. */
7098 {
7099 /* Make a 3-bit mask with the high-order bit being the
7100 value for `>', the next for '=', and the low for '<'. */
7104 {
7106 /* Always false. */
7127 /* Always true. */
7129 }
7134 else
7136 }
7137 }
7138 }
7140 /* If this is a comparison of a field, we may be able to simplify it. */
7145 /* Handle the constant case even without -O
7146 to make sure the warnings are given. */
7148 {
7151 }
7153 /* If this is a comparison of complex values and either or both sides
7154 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
7155 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
7156 This may prevent needless evaluations. */
7163 {
7176 type,
7179 }
7181 /* Optimize comparisons of strlen vs zero to a compare of the
7182 first character of the string vs zero. To wit,
7183 strlen(ptr) == 0 => *ptr == 0
7184 strlen(ptr) != 0 => *ptr != 0
7185 Other cases should reduce to one of these two (or a constant)
7186 due to the return value of strlen being unsigned. */
7191 {
7193 tree arglist;
7205 integer_zero_node));
7206 }
7208 /* From here on, the only cases we handle are when the result is
7209 known to be a constant.
7211 To compute GT, swap the arguments and do LT.
7212 To compute GE, do LT and invert the result.
7213 To compute LE, swap the arguments, do LT and invert the result.
7214 To compute NE, do EQ and invert the result.
7216 Therefore, the code below must handle only EQ and LT. */
7219 {
7222 }
7224 /* Note that it is safe to invert for real values here because we
7225 will check below in the one case that it matters. */
7230 {
7233 }
7235 /* Compute a result for LT or EQ if args permit;
7236 otherwise return T. */
7238 {
7241 else
7246 }
7249 /* Assume a nonexplicit constant cannot equal an explicit one,
7250 since such code would be undefined anyway.
7251 Exception: on sysvr4, using #pragma weak,
7252 a label can come out as 0. */
7259 #endif
7260 /* Two real constants can be compared explicitly. */
7262 {
7263 /* If either operand is a NaN, the result is false with two
7264 exceptions: First, an NE_EXPR is true on NaNs, but that case
7265 is already handled correctly since we will be inverting the
7266 result for NE_EXPR. Second, if we had inverted a LE_EXPR
7267 or a GE_EXPR into a LT_EXPR, we must return true so that it
7268 will be inverted into false. */
7278 else
7282 }
7296 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
7297 so all simple results must be passed through pedantic_non_lvalue. */
7299 return pedantic_non_lvalue
7304 /* If the second operand is zero, invert the comparison and swap
7305 the second and third operands. Likewise if the second operand
7306 is constant and the third is not or if the third operand is
7307 equivalent to the first operand of the comparison. */
7315 {
7316 /* See if this can be inverted. If it can't, possibly because
7317 it was a floating-point inequality comparison, don't do
7318 anything. */
7322 {
7326 /* arg1 should be the first argument of the new T. */
7329 }
7330 }
7332 /* If we have A op B ? A : C, we may be able to convert this to a
7333 simpler expression, depending on the operation and the values
7334 of B and C. Signed zeros prevent all of these transformations,
7335 for reasons given above each one. */
7341 {
7347 /* If we have A op 0 ? A : -A, consider applying the following
7348 transformations:
7350 A == 0? A : -A same as -A
7351 A != 0? A : -A same as A
7352 A >= 0? A : -A same as abs (A)
7353 A > 0? A : -A same as abs (A)
7354 A <= 0? A : -A same as -abs (A)
7355 A < 0? A : -A same as -abs (A)
7357 None of these transformations work for modes with signed
7358 zeros. If A is +/-0, the first two transformations will
7359 change the sign of the result (from +0 to -0, or vice
7360 versa). The last four will fix the sign of the result,
7361 even though the original expressions could be positive or
7362 negative, depending on the sign of A.
7364 Note that all these transformations are correct if A is
7365 NaN, since the two alternatives (A and -A) are also NaNs. */
7372 {
7374 return
7375 pedantic_non_lvalue
7377 negate_expr
7379 arg1))));
7387 return pedantic_non_lvalue
7395 return pedantic_non_lvalue
7399 arg1)))));
7402 }
7404 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
7405 A == 0 ? A : 0 is always 0 unless A is -0. Note that
7406 both transformations are correct when A is NaN: A != 0
7407 is then true, and A == 0 is false. */
7410 {
7415 }
7417 /* Try some transformations of A op B ? A : B.
7419 A == B? A : B same as B
7420 A != B? A : B same as A
7421 A >= B? A : B same as max (A, B)
7422 A > B? A : B same as max (B, A)
7423 A <= B? A : B same as min (A, B)
7424 A < B? A : B same as min (B, A)
7426 As above, these transformations don't work in the presence
7427 of signed zeros. For example, if A and B are zeros of
7428 opposite sign, the first two transformations will change
7429 the sign of the result. In the last four, the original
7430 expressions give different results for (A=+0, B=-0) and
7431 (A=-0, B=+0), but the transformed expressions do not.
7433 The first two transformations are correct if either A or B
7434 is a NaN. In the first transformation, the condition will
7435 be false, and B will indeed be chosen. In the case of the
7436 second transformation, the condition A != B will be true,
7437 and A will be chosen.
7439 The conversions to max() and min() are not correct if B is
7440 a number and A is not. The conditions in the original
7441 expressions will be false, so all four give B. The min()
7442 and max() versions would give a NaN instead. */
7445 {
7450 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
7452 {
7456 }
7459 {
7466 /* In C++ a ?: expression can be an lvalue, so put the
7467 operand which will be used if they are equal first
7468 so that we can convert this back to the
7469 corresponding COND_EXPR. */
7471 return pedantic_non_lvalue
7481 return pedantic_non_lvalue
7490 }
7491 }
7493 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
7494 we might still be able to simplify this. For example,
7495 if C1 is one less or one more than C2, this might have started
7496 out as a MIN or MAX and been transformed by this function.
7497 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
7503 {
7505 /* We can replace A with C1 in this case. */
7512 /* If C1 is C2 + 1, this is min(A, C2). */
7517 return pedantic_non_lvalue
7522 /* If C1 is C2 - 1, this is min(A, C2). */
7527 return pedantic_non_lvalue
7532 /* If C1 is C2 - 1, this is max(A, C2). */
7537 return pedantic_non_lvalue
7542 /* If C1 is C2 + 1, this is max(A, C2). */
7547 return pedantic_non_lvalue
7554 }
7555 }
7557 /* If the second operand is simpler than the third, swap them
7558 since that produces better jump optimization results. */
7564 {
7565 /* See if this can be inverted. If it can't, possibly because
7566 it was a floating-point inequality comparison, don't do
7567 anything. */
7571 {
7575 /* arg1 should be the first argument of the new T. */
7578 }
7579 }
7581 /* Convert A ? 1 : 0 to simply A. */
7584 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7585 call to fold will try to move the conversion inside
7586 a COND, which will recurse. In that case, the COND_EXPR
7587 is probably the best choice, so leave it alone. */
7591 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
7592 over COND_EXPR in cases such as floating point comparisons. */
7599 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7600 operation is simply A & 2. */
7611 /* Convert A ? B : 0 into A && B if A and B are truth values. */
7618 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
7622 {
7623 /* Only perform transformation if ARG0 is easily inverted. */
7628 }
7633 /* When pedantic, a compound expression can be neither an lvalue
7634 nor an integer constant expression. */
7637 /* Don't let (0, 0) be null pointer constant. */
7679 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7680 appropriate. */
7685 {
7689 tree arg01;
7700 {
7714 arg01));
7715 }
7718 }
7721 /* Check for a built-in function. */
7726 {
7730 }
7736 }
7738 /* Determine if first argument is a multiple of second argument. Return 0 if
7739 it is not, or we cannot easily determined it to be.
7741 An example of the sort of thing we care about (at this point; this routine
7742 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7743 fold cases do now) is discovering that
7745 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7747 is a multiple of
7749 SAVE_EXPR (J * 8)
7751 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7753 This code also handles discovering that
7755 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7757 is a multiple of 8 so we don't have to worry about dealing with a
7758 possible remainder.
7760 Note that we *look* inside a SAVE_EXPR only to determine how it was
7761 calculated; it is not safe for fold to do much of anything else with the
7762 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7763 at run time. For example, the latter example above *cannot* be implemented
7764 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7765 evaluation time of the original SAVE_EXPR is not necessarily the same at
7766 the time the new expression is evaluated. The only optimization of this
7767 sort that would be valid is changing
7769 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7771 divided by 8 to
7773 SAVE_EXPR (I) * SAVE_EXPR (J)
7775 (where the same SAVE_EXPR (J) is used in the original and the
7776 transformed version). */
7778 static int
7780 tree type;
7781 tree top;
7782 tree bottom;
7783 {
7791 {
7803 {
7807 /* const_binop may not detect overflow correctly,
7808 so check for it explicitly here. */
7817 }
7821 /* Can't handle conversions from non-integral or wider integral type. */
7827 /* .. fall through ... */
7843 }
7844 }
7846 /* Return true if `t' is known to be non-negative. */
7848 int
7850 tree t;
7851 {
7853 {
7862 /* These are undefined at zero. This is true even if
7863 C[LT]Z_DEFINED_VALUE_AT_ZERO is set, since what we're
7864 computing here is a user-visible property. */
7904 /* Truth values evaluate to 0 or 1, which is nonnegative. */
7906 else
7907 /* We don't know sign of `t', so be conservative and return false. */
7909 }
7910 }
7912 /* Return true if `r' is known to be non-negative.
7913 Only handles constants at the moment. */
7915 int
7917 rtx r;
7918 {
7920 {
7930 {
7932 rtx elt;
7937 {
7941 }
7944 }
7948 /* These are always nonnegative. */
7953 }
7954 }